The use of nanoparticles has enormous potential, in particular for the development of new polymer-based medical products.
Conventional processes for producing nanoparticles are usually based on chemical production methods. Such methods generate nanoparticles typically by conversion of suitable precursor compounds. For example, the precursor compounds can be reacted with an acid, an alkali, a reducing agent or oxidizing agent to give nanoparticles.
An elegant method for production of nanoparticles is that of laser ablation (material removal by laser) in liquids (Amendola et al.: Laser ablation synthesis in solution and size manipulation of noble metal nanoparticles; Phys. Chem. Chem. Phys. 2009, 11, 3805-3821 and Barcikowski et al.: Nanocomposite manufacturing using ultrashort-pulsed laser ablation in solvents and monomers; Polimery 2008, 53, nr 9). Nanoparticles are generated by bombarding substrates immersed into liquid-filled sample vessels with laser radiation. The laser bombardment causes material removal from the substrate surface. The nanoparticles generated are generally the result of nucleation and coalescence phenomena within cavitation bubbles formed above the substrate surface as a result of laser irradiation.
A central problem in generating nanoparticles relates to the agglomeration tendency thereof, as a result of which the further use thereof, especially incorporation thereof into polymeric materials, can be limited in terms of maximum homogeneity of dispersion. An additional factor is that a rise in agglomeration is generally recorded when nanoparticles are subjected to conditions as typically employed in industrial shaping processes, for example, extrusion processes. This is especially true with regard to polymeric materials with high processing temperatures.
One approach to suppressing the unwanted agglomeration tendency of nanoparticles, for example, to achieve maximum homogeneity of “nano-functionalization,” consists of a surface modification of the nanoparticles. However, a difficulty is in developing a suitable surface modification. For instance, in the case of a simple hydrophobic modification of nanoparticle surfaces, there is the risk of separation of nanoparticles and polymer. In the case of a slight surface modification, in contrast, there is the risk that the nanoparticles form unwanted agglomerates, as a result of which a homogeneous “nano-functionalization” likewise cannot be achieved.
WO 2005/070979 A1 describes a chemical production process, based on so-called “emulsion” technology, for polymer-modified nanoparticles.
Chemical production methods for nanoparticles are, however, afflicted with certain disadvantages. For instance, the particle size and the particle size distribution can frequently be controlled only with very great difficulty under the particular chemical conditions. Furthermore; generally time-consuming and costly purification and disposal measures are required for unconverted precursor compounds, reagents and by-products which form. However, impurities are unacceptable especially with regard to medical applications.
The use of laser-generated nanoparticles for production of biologically active devices is known from DE 10 2007 005 817 A1.
It could therefore be helpful to provide modified nanoparticles which avoid known shortcomings and can especially be dispersed very substantially uniformly and homogeneously in polymers.